Method of discharge of electricity into gases.



P. G. COTTBELL. METHOD OF DISCHARGE 0F ELECTRICITY INTOYGASES. APPLICATION FILED NOV. 6, 1911.

11,067,974. Patented July 22, 1913.

WITH/ES SE5.

7?) INVENZOR w W WNI'IED STATES PATENT OFFICE.

. FREDERICK GARDNER COTTRELL, OF BERKELEY, CALIFORNIA, ASSIGNOR TO INTER- NATIONAL PRECIPITATION COMPANY, OF 'LOS ANGELES, CALIFORNIA, A CORPO- RATION OF CALIFORNIA.

METHOD OF DISCHARGE-OF ELECTRICITY INTO GASES.

incanta- Specification of Letters Patent.

Patented Jul 22, 1913..

Application filed November 6, 1911. Serial N 0. 658,657.

To all whom it may concern Be it known that I, FREDERICK GARDNER lo'r'rnELL, a citizen of the United States, re-

siding at Berkeley, in the county of Ala meda and State of California, have invented new and useful Improvements .in the Method of Discharge of Electricity .Into

Gases, of which the following is a specifi-,

stance is described at length in my U. S.

Patent No. 895,729, August 11th, 1908.

Various procedures and apparatus proposed for the .electric deposition of suspended matter from gases have involved the use of collecting electrodes of one constant polarity having a smooth and usually relatively large surface placed in' juxtaposition to discharge electrodes of the opposite polarity usually of smaller surface, as for example, a single Wire or a con-' ductor provided with sharp points, edges, or fine fibers or scales (all of which Will hereafter be generically referred to as discharge electrodes) from which electrical discharge more easily takes place.

One of the simplest possible arrangements of this kind is rep-resented in the accompanying drawing, which is a diagrammatic vertical section of an apparatus suitable for carrying out the process.

In this apparatus is a metallic cylinder serving simultaneously to hold the gas being subjected to discharge and as smooth positive or collecting electrode. The negative discharge electrode (2) is represented as provided with discharge points by a Wrapping (3) of fibrous asbestos twine. This electrode is insulated from the vessel (1) by the non-conducting stopper (4:).

Any suitable source of high potential electricity is conventionally indicated by (5). Gas may be passed through the vessel by means of the inlet (6) and the outlet ('7). A number of such units may be operated in parallel or a plurality of electrodes of both types may be variously grouped in common chambers.

Throughout the patent specifications and other literature on this subject, as far as any choice of actual polarity is in anyway indicated, it appears to be the positive cone ductor from the source of electricity which has been connected to the discharge electrode e. r U. S. Pats. \Valker, No. 342,548,; Thwaitc, NopUlLOlS. As the gases and suspended matter between the electrodes are constantly receiving electricity from the discharge electrodes and as quickly giving it up to the collecting electrodes it is perhaps natural that our recognized convention, whereby electricity is treated as flowing from the positive conductor to the negative, should have led to the assumption that the discharge electrode should be madethe positive In the early laboratory experiments leading up to the process covered by the patent above cited, .it was soon recognizedihat the same eneral effect of deposition of suspended matter upon the collecting electrodes was accomplished whether these were made the positive or negative so long as the discharge electrode had the opposite sign and these polarities were not too rapidly reversed, i. e. as long as the current flowing was essentially direct With theapparatus then at command neither direction of the current was noticed to present any clearly marked advantages over the other. This same conclusion is positively stated by Prof. Oliver 'Lodge in an article in Journal Society Chemical Industry, 557 2-57 6 (1886), which has been the incentive and It seems probably true that about the" same precipitation of dust is effected by an equal quantity of either positive or negative electricity discharged through a given apparatus under the same difference of potential, all other conditions being the same. In operating on a small scale, as in the laboratory, the difference in the ease of control of the discharge from the positive and negative discharge electrodes is a factor of such minor importance that it was at first overlooked. It was not until installations Were undertaken on a larger scale that it was discovered to be'of great practical importance to connect the negative conductor to the discharge electrode and the positive conductor to the collecting electrode.

The chief adtheir fullest attainable capacity where the I vantagein this choice of palarity over that indicated in previous specifications above referred to appears to be that wit-h it a higher potential difference and greater flow of electricity may be maintained between the opposite electrodes without the discharge passing from the silent form to the dis ruptivefi z'. e. sparks or arcs, and 1n.conse-,

conditions above described assume their full significance.

My invention is based on the discovery i that by causing the discharge to pass wholly or mainly from the negative electrode instead of from the positive electrode, the potential difference may be increased without disrupting the dielectric and in carrying out the invention I therefore apply thenegative potential to the electrode whichby reason of its pubescent, pointed, or other special character, is adapted to promote the silent discharge and the potential difference I apply to the electrodes is in excess of that which can be maintained between the electrodes when the-,positivepotentialis applied to the discharging electrodes, other conditions remaining the same Having thus described my invention, what I I claim as new and desire to secure byALetters Patent is v '1. The method of maintaining nondisruptive discharge, at maximum potential, through gases, which consists inapplying a difference of potential to electrode surfaces exposed to the gas, such surfaces being of different character so as to favor discharge in, a given direction through the gas, the negative potential being applied at the surface from which the discharge passes andthe potential difference being in excess of that which can be maintained when the positive potential is applied to said surface.

2. The method of maintaining a nondis- I ruptive discharge at maximum potential through gases, which consists in exposing to the gas a surface facilitating a non-disruptive discharge, and applying to such surface a negative potential, approximating the disrupting potential.

3. The method of separating suspended jecting the gas to the action of a discharging electrode, and maintaining said electrode at a negative potential which is approximately the maximum that can be obtained without particles from gases, which consists in subdisruption of the gas, and is in excess of the positive potential that could be maintained,

under the same conditions, without disruption.

In witness that I claim the foregoing I have hereunto subscribed my name this 31st day of October 1911. 7 FREDERICK GARDNER .QOTTRELL. Witnesses: l

WALTER EATON, D. -B. RICHARDS. 

